{"slug": "smart-home-garden-irrigation-project", "title": "Smart Home Garden Irrigation Project", "summary": "A mechanical engineer has built a bespoke smart garden irrigation system for under £10 per zone using 12V solenoid valves, a WiFi relay, and Home Assistant. The system features normally closed valves for safety, one solenoid per zone for full water flow, and sequenced zone operation to ensure adequate pressure. The project emphasizes modularity, standard components, and low-cost DIY construction.", "body_md": "##\nGarden Irrigation System\n\n##\nSummary\n\nMY project to make a bespoke irrigation system for my home garden, which comes in at under £10 per zone including the actual water delivery method, and is made with relatively easily sourced components. I am a mechanical engineer by training, but not an electrician so interested in hearing pointers on how to make it better.\n\nSome of the component and tool links below are AliExpress affiliate links. If you buy through them I earn a small commission at no extra cost to you. Everything listed is what I actually bought and used, or the closest equivalent I could find. This helps me fund some more ambitious but hopefully useful builds in the future.\n\n##\nIntro\n\nSo I have a vegetable patch and some flowers in the garden; it became a bit of a job during the hot days of summer to water the plants in the evening. I didn’t especially mind it but given my love of AI and tech, alongside recent experiments with Home Assistant, I thought there must be a 2026 version of this job. I tried a Wi-Fi-controlled tap, but quickly realised the flow rate was low - due to a small aperture size, and also scaling up with this type of solution to 6 + zones would quickly get expensive and leave me dependent on battery-powered solutions - also not a big win. So as I had begun experimenting with creating my own devices with dev boards etc, I figured, “how hard can it be” and in honesty it wasn’t, just took a bit of trial and error. This guide will be focused on how i would build it today, not all the steps that got me to here.\n\n##\nMy philosophy\n\nStandardised equipment/ components as much as possible\n\nSpeed of delivery = speed of experimentation\n\nModular where possible\n\nAnything can be achieved at any cost, but some of the fun is building something from very little\n\n##\nComponents\n\nNote all water pipes for this project are ½ inch and so connector etc are for that, this corresponds to a ¾ in threaded connector for attaching to pipes\n\n##\nTools\n\n##\n**How it works**\n\nThe water path is simple: outside tap, 4 way splitter, one 12V solenoid valve per zone, soaker hose in each bed. The electrical path sits alongside it: a 12V power supply feeds a fused distribution block, a WiFi relay switches the 12V feed to each solenoid independently, and Home Assistant decides when each channel goes on.\n\nFour decisions do most of the work here:\n\n-\n**Normally closed valves.** No power means no water. If the relay dies, the WiFi drops, or the PSU is unplugged, the garden stays dry rather than flooding.\n-\n**12V, not mains.** Everything outdoors runs at 12V DC, so the only mains item is the plug-in PSU and that stays in a waterproof plug box. Much less to worry about in a wet plastic box.\n-\n**One solenoid per zone, not one smart tap.** A full bore 3/4 inch solenoid passes far more water than the pinhole aperture in a battery tap timer, and at roughly 3 pounds a valve, adding a zone is cheap.\n-\n**Zones run one at a time.** A domestic outside tap will not feed four soaker hoses at once. Sequencing in Home Assistant gives every bed full pressure for its slot.\n\n##\n**Build order**\n\nDo the electrics on the kitchen table first, then the plumbing outside. It is much easier to find a bad crimp indoors than crouched behind a water butt.\n\n###\n**1. Wire the control box**\n\n- Cut the 5.5 x 2.1 female pigtail to length. Positive goes through the 5A fuse into the fuse box input stud, negative goes to the negative busbar. Fork crimps on both studs.\n- Fit a 1A fuse per zone in the fuse box. Each fused output feeds the COM terminal of one relay channel.\n- The NO terminal of each channel becomes the positive leg of that zone's outdoor run.\n- Take the relay module's own supply from the fuse box as well, on its own fused way. Check your module's input range covers 12V before you power it, most are 7 to 32V DC.\n- Ferrule every stranded end that goes into a screw terminal. Ferrules are the difference between this working for three seasons and working for three weeks.\n- Label the four outputs before you close the box. You will not remember which is which in April.\n\n###\n**2. Run the zone cables**\n\n- 18 AWG two conductor cord from the box out to each valve. Keep colour convention consistent even though solenoid coils are not polarity sensitive.\n- Terminate each run with one half of a waterproof two pin connector, and put the other half on a short tail with spade connectors for the valve terminals.\n- That connector is worth the effort: it lets you unplug and swap a valve without cutting or rejoining anything.\n- Don’t do what i did first time - those waterproof 2 wire plug connectors DO NOT need you to strip the wire before inserting in the round apertures. Literally cut to lend insert in the connect and clip shut with pliers and they cut through the insulation to the wire for you.\n\n###\n**3. Drill and mount the housing**\n\n- 18mm hole for the incoming DC lead and the zone cables - I used a PG13.5 gland for this which will bolt into the 18mm hole.\n- Drill entries on the underside or a side face, never the top. Water finds every hole you make above the horizontal. I put the gland in the side for the controller box and the solenoid box.\n- For the solenoid box you need 1x18mm hole for the PG13.5 cable gland + 4 x 18mm holes for the hoses - I didnt use glands for the hoses, but you could - I’d recommend PG25 glands for those - you can check thew drilliam diameter- i think its 27mm.\n- In addition for the solenoid box i drilled holes in the bottom so if a hose leaks the box can drain and not flood.\n- I stacked the controller box on top of the solenoid box, so if a hose bursts it’s less likely to flood the controller box.\n- The PSU stays indoors or in a waterproof plug box. Only the 12V extension leaves the house.\n\n###\n**4. Plumb the zones**\n\n- Threaded tap connector onto the outside tap, and a length of hose to reach where you want to water and then add the 4 way splitter onto that.\n- Short length of hose from each splitter outlet to the inlet side of a solenoid, using the push fit connector pairs.\n- Check the flow arrow on each valve body. These are directional and a backwards valve will not open reliably.\n- Valve outlet to a length of hose extending to the bed, and connect the soaker hose for that bed.\n\n###\n**5. Home Assistant**\n\n- Pair the relay in Smart Life, then add the Tuya integration in Home Assistant. You should end up with four switch entities.\n- Rename them by bed rather than by channel number.\n- Build the watering run as a sequential automation so only one zone is ever open.\n\nAdd a second automation as a backstop: if any zone switch has been on for longer than 15 minutes, turn everything off. Automations get interrupted by restarts and updates, and an open valve overnight is an expensive way to learn that.\n\n###\n**6. Test before you trust it**\n\n- Continuity check every run with the multimeter before the valves go on.\n- Power up dry and switch each channel from Home Assistant. You should hear each solenoid click.\n- Turn the tap on and run each zone alone, checking every joint for weeping.\n- Run one full cycle while you watch it, then check for puddling and adjust the per zone duration.\n\n##\n**Winter**\n\nNormally closed valves cannot be left open to drain, so before the first frost: turn the tap off, disconnect the valves and store them inside, and bring the PSU and relay in with them. Leave the soaker hoses in place but disconnected at the splitter so they can drain.\n\n##\n**Where I would take it next**\n\n- Swap the Tuya relay for an ESP32 running ESPHome with a relay board, which removes the cloud dependency and lets the schedule survive an internet outage.\n- Add a soil moisture sensor per bed and water on a reading rather than a clock.\n- Add a flow sensor on the inlet so Home Assistant can tell the difference between a zone that ran and a zone that thought it ran.", "url": "https://wpnews.pro/news/smart-home-garden-irrigation-project", "canonical_source": "https://dev.to/david_02n/smart-home-garden-irrigation-project-40p2", "published_at": "2026-08-28 21:41:16+00:00", "updated_at": "2026-08-28 21:48:20.135146+00:00", "lang": "en", "topics": ["developer-tools", "ai-products"], "entities": ["Home Assistant", "AliExpress"], "alternates": {"html": "https://wpnews.pro/news/smart-home-garden-irrigation-project", "markdown": "https://wpnews.pro/news/smart-home-garden-irrigation-project.md", "text": "https://wpnews.pro/news/smart-home-garden-irrigation-project.txt", "jsonld": "https://wpnews.pro/news/smart-home-garden-irrigation-project.jsonld"}}